The recent technological revolution in cosmetic bonding for dental restorations has provided a myriad of ceramic-resin systems. Materials have become more sophisticated, exhibiting better resistance to wear, better crushing strength, and better ability to seal or bond to both enamel and dentin tooth structure.
The restorative composite resin materials that are used for posterior dental restoration include a Bis GMA resin or urethane dimethacrylate resin with various sized and shaped hard filler particles of ceramic, quartz or glass material. The hard filler particles presently being used include: quartz, barium glass, silica glass, agglomerated silica complexes, silica pellets, zeolite, strontium glass, RCMS (resin capped micro silica), barium aluminum silicate glass, lithium aluminum silicate glass and zinc glass. The percent load of hard filler material varies according to particle size, shape and manufacturers' specifications.
Many problems in the use of these materials in the posterior regions of the mouth have been overcome. Prior to this invention a perplexing problem has continued to exist in establishing firm and properly located interproximal contact when using the new composite ceramic-resin technology, in spite of the various innovative matrix systems which recently have been developed.
During fabrication and insertion of a dental restoration with composite ceramic-resin materials, a matrix band is used to hold the restorative material within a cavity prepared in the tooth being restored. A gingival wedge commonly is used with the matrix band to force the adjacent teeth apart and to hold the matrix band tightly against the tooth being restored, at the gum line. The restorative material is then inserted and hardened, and afterwards the matrix band is removed. However, when the matrix band and gingival wedge are removed and the separation pressure is relieved, a space may remain between the restoration and the adjacent tooth. Food particles become lodged in that space and eventually cause tooth decay and/or gum disease.
Conventional matrix and wedging techniques call for very thin matrix bands and various forms of extra coronal gingival wedges. The separation afforded by gingival wedge pressure has been thought to overcome the interproximal gap created by the matrix band after restoration is complete. In spite of ever thinner matrices (0.0015 or 0.0010 inches), subsequent to composite restoration, weak or open contact has been common.
Food particles can collect in these spaces. Additionally, the plasticity of the composite materials before curing makes it difficult to obtain the desired contour of the restored tooth. The composite materials may be self-curing or light-cured. However, with the preferred light-cured composites, it is sometimes difficult to cure the composite material in the deeper recesses of the cavity.
Further, studies of wedge efficiency and separation show that the most common brands of wooden wedges experience wedge fatigue, with corresponding loss of original apparent separation, after only about four minutes of use. Unyielding plastic or other wedges made from hard non-compressible materials are more efficient separators and do not fatigue, but often do not "grip" well and slide or loosen during tooth and restorative manipulation. Hard, non-yielding and non-fatiguing wedges also do not properly hold the matrix well against the irregular cervical root anatomy. As a result, use of these hard wedges allows overhangs and poor gingival margin adaptation in the cured restoration.
In contrast to composite resin restoration, traditional silver amalgam restoration, when inserted after proper gingival wedging, provides auxiliary wedging and separation. The auxiliary wedging and separation of the amalgam restoration is due to the compactibility of the amalgam and its ability to stay where it is placed and to be condensed with significant pressure causing a lateral force vector against the adjacent tooth. This additional separation is crucial to establishing a successful contact, which is routinely obtained in amalgam restorative systems. The currently available composite resin techniques heretofore do not allow such routine success. Table 1 shows a typical test result using a wooden gingival wedge and silver amalgam. Prior to this invention, auxiliary wedging was not possible through condensation of composite resin materials, no matter how highly filled or stiff these materials have been.
Accordingly, it is an object of this invention to provide a device which will establish firm and properly located interproximal contact relationships with composite resin restorative materials.
A further object of this invention is to provide an easy, predictable method for establishing proper interproximal contact pressure and anatomic form with a composite resin restoration.
Another object of this invention is to provide a device for establishing static contour relationships with matrix systems to provide the necessary interproximal separation when using composite resin restorative material.
An additional object of this invention is to provide a device which reduces the thickness of the composite resin material to be cured by light catalysis in order to insure more complete curing of the deeper recesses of the cavity preparation.
Additionally, a further object of this invention is to decrease the bulk of restorative resin to be cured to eliminate the disadvantages inherent in linear and volumetric shrinkage of the material during setting.
TABLE 1 ______________________________________ Test Results Using Wooden Gingival Wedge and Silver Amalgam (See FIG. 9) INTER- PROXIMAL SEPARATION STEP (INCHES) COMMENTS ______________________________________ Separation at initial 0.0000 reference point (11) Separation after wooden +0.0010 wedge inserted After 4 minutes with +0.0006 Teeth moved wooden wedge closer After teeth are rewedged +0.0013 More forcefully separation After amalgam has been +0.0019 Lateral inserted and condensed/packed component of into the cavity forces of packing transferred from packing instrument to the amal- gam pushes on side of adjacent tooth caus- ing more separation, restored tooth moves away from adjacent tooth After wedge removed +0.0003 Close to optimum separation slight over contact pressure al- lows strip finishing ______________________________________